Splanchnology (SPLANCHNOLOGIA) - the science of internals

The internals - the internal organs that lie in body cavities (mouth, cavity of neck, chest, abdominal, pelvic) and provide the metabolic processes in the organism with the external environment. The internals are combined into organs systems (digestive, respiratory, urogenital).

Development of internals

After 3th week of fetal development, as a result of end of gastrulation are formed three germ layers (ectoderm, mesoderm, endoderm) and axial complex of germs. Mesoderm is divided into:- dorsal- intermediate- ventral.

Ventral mesoderm is divided into visceral and parietal. Actually with of visceral mesoderm and endoderm is formed the primary intestine, from which develop digestive and respiratory systems. Primary intestine formed at 3-4th weeks of fetal development and consists of two layers: internal - endoderm, external - visceral mesoderm. Of primary intestine endoderm develops epithelium and glands of the digestive and respiratory tracts, of visceral mesoderm - serous membrane epithelium; all other layers of organs develop from the mesenchyme (embryonic connective tissue, which is a derivative of visceral and parietal mesoderm). Primary intestine has 3 sections: front, middle and rear. Primary intestine ends blindly in the main and caudal ends of the embryo. In the 4-5-week-old embryos in the head and in the caudal part of the body appear two holes that gradually go deep to meet of primary ends of the blind intestine, then intrudingby creating mouth and cloacal openings of primary intestine. Cloaca is divided with time to anal and urogenital openings.

Parietal mesoderm adjoins to inner surface of the body wall. Between the parietal and visceral mesoderm is formed internally embryonic body cavity. At 3-5th week continuous internally embryonic body cavity is divided into sections by three walls.Urogenital system develops from intermediate mesoderm.

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